Compiling fails: file missing but it's there

I try to compile xf4vnc on Lenny AMD64 following this page:
http://xf4vnc.sourceforge.net/modular.htmlOnly compiling the xserver fails. It complains about missing pixmap.h
file. The file is installed via aptitude
("/usr/include/pixman-1/pixman.h") and when trying "make install" it
seems to look in the right directory because "-I/usr/include/pixman-1"
is visible.